drm/i915: probe lmem before the stolen portion

At the very least, we have some tests that force the BAR size for
testing purposes, which would result in different BAR size with
stolen-lmem vs normal lmem, since the BAR is only resized as part of the
normal lmem probing.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230127160321.374350-1-matthew.auld@intel.com